no sound from either microphone, USB, or directly into computer.

I have had a large sound system , one active(pink and green) and one yellow plug in which goes back to rear of computer.

There IS sound from the computer directly, via these large speakers. For example,I can play and hear music, like my favourite "Apache" which is definitely heard, as is Skype's "Echo".

This has worked for many years, but I now think it has died of old age.
So I tried various other options - microphone on stand(USB)headphone with pink and green plug-ins and over the head standard USB.

Nothing is working. Is it possible that sounds which were on the computer itself have all broken.